Achieving nearly uniform light distribution about a light bulb has long been a goal in the lighting industry. Success in this goal has largely depended upon the method of providing light employed by the bulb. Specifically, different methods of light generation produce light with different distributions, which must be compensated for in the construction of the bulb.
Most of the earliest light bulbs were incandescent, which generate light by heating a filament wire until it glows. Due to the relatively sparse nature of the supporting structures necessary for the filament, and due to the 360-degree dispersion of light by the filament, achieving nearly uniform distribution about an incandescent light bulb was not difficult to achieve. However, due to inefficiencies in the method of light production employed in incandescent light bulbs, other methods are desirable.
Fluorescent lamps, specifically compact fluorescent lamps (CFLs), have been steadily replacing incandescent light bulbs in many lighting applications. Similar to incandescent, CFLs produce light in approximately 360 degrees by exciting mercury vapor to cause a gas discharge of light. CFLs are more energy efficient than incandescent light bulbs, but suffer a number of undesirable traits. Many CFLs have poor color temperature, resulting in a less aesthetically pleasing light. Some CFLs have prolonged warm-up times, requiring up to three minutes before maximum light output is achieved. All CFLs contain mercury, a toxic substance that must be handled carefully and disposed of in a particular manner. Furthermore, CFLs suffer from a reduced life span when turned on and off for short period. Therefore, there are a number of disadvantages to using CFLs in a lighting system.
Light emitting diodes (LEDs) are increasingly being used as the light source in light bulbs. LEDs offer greater efficiencies than CFLs, have an increased life span, and are increasingly being designed to have desirable color temperatures. Moreover, LEDs do not contain mercury or any other toxic substance. However, by the very nature of their design and operation, LEDs have a directional output. Accordingly, the light emitted by an LED may not have the nearly omni-directional and uniform light distribution of incandescents and CFLs. Although multiple LEDs can and frequently are used in a single light bulb, solutions presented so far do not have light distribution properties approximating or equaling the dispersion properties of incandescents or CFLs. Accordingly, there is a long felt need for a light bulb that can utilize LEDs as a light source while maintaining uniform and nearly omni-directional light distribution properties.
One issue facing the use of LEDs to replace traditional light bulbs is heat. LEDs suffer damage and decreased performance when operating in high-heat environments. Moreover, when operating in a confined environment, the heat generated by the LED and its attending circuitry itself can cause damage to the LED. Heat sinks are well known in the art and have been effectively used to provide cooling capacity, maintaining an LED-based light bulb within a desirable operating temperature. However, heat sinks can sometimes negatively impact the light distribution properties of the light bulb, resulting in non-uniform distribution of light about the bulb. Accordingly, there is a long felt need for an LED-based light bulb capable of providing uniform light distribution that maintains a desirable operating temperature.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.